JP6325483B2 - Method and apparatus for regenerating a catalytic diesel particulate filter (DPF) by active NO2 utilization regeneration with enhanced effective NO2 supply - Google Patents

Description

The present invention relates to a method and apparatus for regenerating a diesel particulate filter (DPF), ie, removing accumulated particulate matter or soot from the DPF, and more particularly to a method and apparatus involving an oxidation reaction with NO ₂ .

The present application is filed on the same day as the present application and has the same assignee, and is a co-pending application PCT / US2009 entitled “Method and Apparatus for NO ₂ Utilization Regeneration of Diesel Particulate Filters Using Recirculated NOx”. 2009, named “Method for Maximizing NO ₂ Reactant Smoke Reducing Capacity for Active NO ₂ Regeneration of Particulate Filters” in relation to No. 033512 (Attorney Docket No. 000009-261) Claims priority of US Provisional Application No. 61 / 063,900, filed February 7,

The most common method for removing soot from DPF is the oxidation of trapped soot to generate gaseous products (CO ₂ and CO) that can pass through the filter media, a process called regeneration. There are two The main mechanism to be used for reproduction, the oxidation of soot by _{O 2} called _{O 2} based regeneration _{((C + O 2 → CO} 2) and / or _{(2C + O 2 → 2CO)} ), NO 2 based regeneration Oxidation of soot by NO ₂ ((C + 2NO ₂ → CO ₂ + 2NO) and / or (C + NO ₂ → CO + NO)).

Currently known and practiced solutions for DPF regeneration include active O ₂ utilizing regeneration systems, passive NO ₂ utilizing regeneration systems, or combinations thereof. Active O ₂ utilizing regeneration systems raise the temperature of the reactants in a variety of ways to establish and maintain the O ₂ / smoke reaction. During active O ₂ utilization regeneration, substantially all soot removal is due to reaction with O ₂ . A passive NO ₂ utilization system is generally used for generating NO ₂ from NO already present in the exhaust gas in an oxidation catalyst upstream of the DPF and for normal engines without active thermal management of the reactants. Catalytic agents are used to reduce the activation energy required to generate a NO ₂ / smoke reaction at a temperature level that can be achieved in part of the operating range.

Many implementations have been demonstrated for the concepts of active O ₂ utilization and passive NO ₂ utilization for DPF regeneration. The main limitation of passive NO ₂ utilization regeneration is that proper regeneration of DPF cannot be guaranteed in all applications. In order to solve this, active O ₂ utilization regeneration is performed instead of or in addition to passive NO ₂ utilization regeneration. The main limitation of O ₂ utilization regeneration is that the maximum DPF soot collection level that must be observed is low and the temperature requirement is significantly higher than that required for NO ₂ utilization regeneration. In addition to the need for more frequent regeneration, high temperature requirements lead to reduced performance and durability of all affected exhaust aftertreatment devices, including those downstream of soot filtration regeneration components such as SCR systems Sometimes. Solving the temperature problem must be done by developing more robust aftertreatment devices and / or implementing additional devices, systems, and / or methods that lower the temperature behind the DPF.

Several methods have been proposed to supplement the concept of active O ₂ utilization and passive NO ₂ utilization regeneration. Patent Document 1 discloses a method of initiating an alternative control strategy appropriate reactant temperature makes the generation of passively established optimum NO _x during operation. Patent Document 2, in order to extend the operation period appropriate passive NO ₂ based regeneration activity is achieved, the reaction temperature and the DPF volumetric flow rate (and thus DPF residence time) describes a method which is actively operated ing.

US Patent Application Publication No. 2007/0234711 US Pat. No. 6,910,329

According to an aspect of the present invention, a method for regenerating a catalytic diesel particulate filter (DPF) by active NO ₂ utilization regeneration with enhanced effective NO ₂ supply includes introducing a NOx-containing gas into the DPF, NOx-containing gas, while controlling at least one temperature of soot in the DPF, NOx-containing gas reacts with the catalyst, after the CO to react with soot particles, the NO ₂ molecules to generate a _CO 2, NO molecules generated and, NO ₂ efficiency to be higher than 0.52gC / gNO _2, and _O are oxidized by ₂ molecules CO and CO ₂ molecules in less than 2 gas thirds of soot mass that is removed from the DPF To control the NOx level at the entrance of the DPF.

According to yet another aspect of the present invention, a diesel engine mechanism includes a diesel engine configured to introduce a NOx-containing gas into a catalytic diesel particulate filter (DPF), a DPF, a NOx-containing gas, and soot in the DPF. A heating mechanism configured to control at least one temperature of the gas, and a NOx-containing gas reacts with the catalyst to generate NO ₂ molecules that subsequently react with the soot particles to produce CO, CO ₂ , NO molecules NO ₂ efficiency to be higher than 0.52gC / gNO _2, also less than two thirds of the soot mass that is removed from the DPF to generate has been CO and CO ₂ molecules oxidized by _{O 2} molecules in the gas with by controlling the NOx levels at the inlet of it and DPF for controlling the temperature, by controlling the heating mechanism, active effective NO ₂ supplied strengthen Including a controller configured to implement the NO ₂ based regeneration.

According to yet another aspect of the present invention, a method for regenerating a diesel particulate filter (DPF) includes introducing a NOx-containing gas into a DPF and reacting the NOx-containing gas with a catalyst and subsequently reacting with soot particles. Te CO, generates NO ₂ molecules to generate a _CO 2, NO molecules, as NO ₂ efficiency is higher than 0.52gC / gNO _2, or 3 minutes less than 2 gases of soot mass that is removed from the DPF and controlling at least one of the temperature of the soot of the DPF and NOx-containing gas and the DPF while controlling the NOx levels of O is oxidized by ₂ molecules at the inlet of the DPF so as to produce CO and CO ₂ molecules in Performing a first regeneration that at least partially regenerates the DPF by performing an active NO ₂ utilization regeneration with enhanced effective NO ₂ supply, including Including performing a _second regeneration that at least partially regenerates the DPF by performing at least one of a _two- use regeneration and an active O ₂ use regeneration.
The features and advantages of the present invention will be better understood by reading the following detailed description in conjunction with the drawings in which like numerals refer to like elements.

FIG. 2 schematically illustrates a partial cross-sectional view of a portion of a DPF passage wall depicting NO recirculation according to an embodiment of the present invention. If it is more shows the balance line NO ₂ is converted to NO, a graph of the NO ₂ conversion efficiency and temperature of the samples diesel oxidation catalyst at various exhaust mass flow (DOC). Conventional NO ₂ usage reproduction, compared to the active NO ₂ based regeneration of the active NO ₂ supplied reinforced in accordance with aspects of the present invention, it is a graph of the reproduction time soot trapped amount. It is a table | surface of the data shown as a graph by FIG. 3A. 1 schematically illustrates an exhaust aftertreatment system according to an aspect of the present invention.

  The invention will be described first with a general and more theoretical expression as understood by the inventors at the present time, and then with respect to more specific embodiments. The theory presented to explain what the inventors currently understand about how the invention works is not intended to limit the invention, except as expressly included in the claims. Unthinkable.

  The inventors recognize that there are two situations where the reaction rate of soot in the DPF is limited. The reaction is either reaction rate dominant (by reactant temperature too low) or diffusion limited (by reactant feed rate too low). Briefly, the necessary reactants must be supplied and the minimum activation energy of the reaction must be reached. These conditions are met by active control or passively achieved during normal operation.

Any type of active regeneration process that utilizes active thermal control raises the temperature of the reactants to a point where a reaction rate sufficient for the desired reaction is established. Filter medium, exhaust gas, and / or trapped by external means (by catalytic catalytic oxidation of hydrocarbons, burner system, electric heating, microwave, etc.) until above normal operating temperature that is insufficient to support regeneration This is generally achieved by raising the temperature of the soot. In the active regeneration process, active control of the reactant feed may be implemented, but this is not done. For example, O ₂ -based regeneration has a large amount of O ₂ subject to reaction rate, but conventional NO ₂ strategies generally do not actively regulate the NO ₂ or NO x supply.

By definition, a passive regeneration system does not actively control reactant temperature or reactant supply for the purpose of promoting regeneration. However, some passive means are used to promote regenerative activities. That is, a catalytic agent in contact with trapped soot, such as a catalyst coating in the DPF, is used to reduce the activation energy (temperature) required for the associated reaction, thereby controlling the reaction rate. Reduce (allows high reaction rate). If there is a sufficiently high reaction temperature to do more than support full reaction of all reactants, the reaction is diffusion limited. In the case of DPF full of soot, a diffusion limited reaction means that the supply of oxygen-containing reactant is limited. Therefore, the catalyst is used to passively increase reactant supply, such as converting unusable NO to beneficial NO ₂ , thereby reducing the diffusion limitation of the reaction (ie enabling high reaction rates). To do).

煤煙捕集密度、煤煙酸化速度、煤煙発生との間の関係には、いくつかの因果関係が存在する。（温度および反応物供給を含む再生条件がすでに安定している）安定した再生プロセスについては、再生事象の開始時に最高の煤煙酸化速度および煤煙除去速度が達成されている。再生が進行するにつれて煤煙酸化速度は低下して、ついに最後には煤煙発生速度と交差し、このポイントで煤煙除去速度はゼロに等しくなる。結果的に、能動的Ｏ_２利用再生を含むすべての再生プロセスは、ゼロではない平衡煤煙捕集量に近づく。特に効果的な戦略では、ほぼ完全な煤煙再生に近づくかもしれないが、到達することはない。 In considering the practical application of soot oxidation process, i.e., soot removal from DPF, a distinction must be made between reaction rate, soot oxidation rate, engine soot generation rate, soot removal rate. Starting with the practical goal of DPF soot removal, we will return to the more essential and theoretical concept of chemical kinetics. The smoke mass removal rate is simply the change in DPF smoke mass over time. The soot removal rate is not constant during the regeneration event because it correlates with the trapped soot mass that varies with time. The soot removal rate is equal to the difference between the soot oxidation rate and the engine soot generation rate. Equation 1 shows the soot mass in the DPF as a function of time.

There are several causal relationships between the soot collection density, soot oxidation rate, and soot generation. For a stable regeneration process (regeneration conditions including temperature and reactant feed are already stable), the highest soot oxidation rate and soot removal rate are achieved at the start of the regeneration event. As regeneration proceeds, the soot oxidation rate decreases and finally crosses the soot generation rate, at which point the soot removal rate is equal to zero. As a result, all regeneration processes, including active O ₂ utilization regeneration, approach non-zero equilibrium soot collection. A particularly effective strategy may approach but not reach near-perfect soot regeneration.

ｍ＝煤煙質量
Ｃ＝定数
［ＮＯ_２］＝反応に関与するＤＰＦ内のＮＯ_２の濃度
Ｔ＝反応温度
Ｅ＝活性化エネルギー
Ｒ＝普遍気体定数
アルファ、ベータ、ガンマは指数である。 The soot oxidation rate expressed in Equation 2 is equal to the trapped soot mass multiplied by the chemical reaction rate. The reaction rate is primarily a function of the temperature and amount of NO ₂ involved in the reaction, which is the NO ₂ feed rate, the soot mass, and on average one NO ₂ molecule contains two or more C atoms. This is a function of the number of recycles when “recycle” is defined as being involved in the oxidation reaction. Since recirculation is a NO oxidation reaction, the number of recirculations is mainly determined by the NO oxidation reaction rate and residence time. The NO oxidation reaction rate is primarily a function of temperature, reactant effectiveness and catalyst effectiveness.

m = smoke mass C = constant [NO ₂ ] = concentration of NO ₂ in the DPF involved in the reaction T = reaction temperature E = activation energy R = universal gas constants alpha, beta and gamma are exponents.

The regeneration process mainly involves surface reactions between the heterogeneously dispersed solids and, moreover, (generally) gaseous reactants that must be in contact with the catalyst. Therefore, the chance that moving oxygen-containing gas particles will find (immediately) stationary (and heterogeneously dispersed) soot particles that are also in the presence of a stationary solid catalyst increases as soot density increases. It will be. Therefore, more reactions will occur once as the smoke collection density increases. This is true for most if not all reaction rate limited regeneration processes. The inventors recognize that this is the case for most if not all diffusion limited reactions in which the limiting reactant is recycled. NO in a state in which the catalyst 10 is present reacts with _{O 2} to generate NO ₂ to DPF 11, NO ₂ reacts with soot 12 of the DPF generating and NO + CO + CO _2, NO in the presence of a catalyst _{O 2} A recirculation phenomenon is schematically illustrated in FIG. 1 by reacting again with NO to produce NO _{2 and the} like, and finally NO or NO ₂ exits the system. For diffusion limited reactions where the limiting reactant cannot be recirculated or is abundant soot that does not recirculate, it is generally not true that more reactions occur at once as the soot collection density increases. Are aware. In this case, all of the limiting reactant is already consumed and not reused, so the maximum number of reactions has already occurred. Consequently, the method according to aspects of the present invention has the advantage over conventional NO ₂ usage, i.e., regeneration effect and NOx efficiency as soot trapped amount increases will rise significantly.

NOx present in diesel exhaust gas include predominantly NO, including only slightly NO _2. As such, in a passive regeneration system, a catalytic agent such as a diesel oxidation catalyst (DOC) is commonly used to generate NO ₂ from NO.

It is usually desirable to increase the achievable passive NO ₂ utilization regeneration activity for a given amount of NOx by increasing the NO ₂ / NO ratio to increase total NO ₂ or the amount of reactants. In other words, it is the usually desirable to increase the reaction rate of the soot in the DPF by increasing the supply amount of the limiting reactant NO _2. However, as can be seen in FIG. 2, for a given exhaust mass flow rate, the catalyst's effect during the conversion from NO to NO ₂ begins to increase with increasing temperature first and then decreases with NO−. It descends along the NO ₂ equilibrium line. Once the equilibrium line is traced, the NO ₂ supply amount becomes the equilibrium limit. The actually measured NO ₂ supply that is equal to or less than the equilibrium limit shall be referred to as the “equilibrium limited NO ₂ supply”.

Equilibrium-limited NO ₂ supply is relevant for systems that include or do not include a catalyst agent upstream of the DPF. In the case of a system with an effective catalyst agent upstream of the DPF, the equilibrium limited NO ₂ supply will refer to the actual amount of NO ₂ produced upstream of the DPF and sent to it. For systems with a catalyst agent upstream of the DPF, the catalyst agent must act to substantially increase the NO ₂ supply of NOx-containing gas during the regeneration event, otherwise, the equilibrium limited type It goes without saying that the system is considered not to have a catalyst agent upstream of the DPF in determining the NO ₂ supply. Regeneration also occurs when the amount of NO ₂ available from the catalyst agent to the DPF is significantly less than the NO ₂ exiting from the DPF when there is no NO ₂ involved in the soot oxidation reaction, as in the case of DPF without soot. It is believed that the catalyst agent does not act to significantly increase the NO ₂ supply during the event. In the case of a system in which NO ₂ is generated by catalytic DPF without a catalyst agent upstream of DPF, the equilibrium-limited NO ₂ supply amount is determined as NO released from DPF when there is no NO ₂ involved in the soot oxidation reaction. Refers to the amount of ₂ .

During passive NO ₂ regeneration, the soot oxidation reaction is kinetically controlled or diffusion limited. In the case of a fully collected DPF, the type of restriction depends not only on the reactant temperature, but also on the amount of NO ₂ supplied to the reaction.

A rate-dominated NO ₂ / smoke reaction means that all of the NO ₂ that has passed through the DPF does not react while in the DPF, but is therefore “waste”. Unlike O _{2 in} the case of active O ₂ utilization regeneration, NO ₂ (and NOx) is a regulated emission, so unnecessary generation of NO ₂ that is not involved in soot regeneration should be avoided.

Alternatively, a diffusion-limited NO ₂ / smoke reaction means that the amount of NO ₂ supplied is less than what can react within a given residence time at ambient temperature. Similarly, if the reaction is diffusion-limited by soot, this means that DPF soot collection is low. The time that the reactant (NO ₂ ) spends in the reactor (DPF) is called residence time. In the case of a diffusion-limited reaction, the soot regeneration is completed in a short time as the NO ₂ supply amount increases. In a passive NO ₂ utilization regeneration event, the optimal amount of NO _x will generate an equilibrium limited NO ₂ supply that is approximately matched to the kinetic reaction rate at ambient temperature. Therefore, the reaction will approach the equilibrium point between the reaction rate dominant and diffusion limited types. For this purpose, an active NO ₂ utilization regeneration concept may be devised that actively controls the temperature and / or feed rate and / or residence time of the reactants. These approaches, whether performed passively or actively, will be referred to as “conventional” NO ₂ utilization regeneration concepts. The conventional NO ₂ utilization regeneration concept will maximize the NO ₂ / smoke reaction rate by optimally approaching the equilibrium point between reaction rate and diffusion limitation.

Regardless of whether it is recognized or not, the conventional NO ₂ utilization regeneration method allows NOx to be supplied to the reaction as long as the equilibrium point between the reaction rate-dominated and diffusion-limited soot oxidation reactions is achieved. _By increasing the percentage by ₂ ("NO ₂ percent") in an optimal manner and / or adjusting the reactant temperature in an optimal manner, it is intended to increase the soot regeneration effect and / or efficiency. . If it is intended to increase the NO ₂ percent to be supplied to the reaction in the conventional method, this is achieved by increasing either the potential equilibrium NO ₂ percent NO ₂ percent or in DPF is supplied to the DPF The potential equilibrium NO ₂ percent is determined by the supply of a mixture of NO and NO ₂ to the DPF, the ambient conditions within the DPF, and by the NO-NO ₂ equilibrium relationship.

The inventors have recognized that the method according to aspects of the present invention can achieve a higher soot regeneration effect or efficiency than conventional methods. The inventors recognize that the amount of NO ₂ that reacts with soot is much greater than the amount of NO ₂ fed to the reactor (DPF). Furthermore, the inventors recognize that the amount of NO ₂ that reacts with soot within a given time is still greater than the theoretical equilibrium amount of NO ₂ that passes through the reactor within the same time. In the method according to the aspect of the present invention, even if the NO ₂ concentration supplied to the DPF and the equilibrium NO ₂ concentration in the DPF are decreased, the method reacts with the smoke by increasing the smoke oxidation reaction rate and the NO oxidation reaction rate. increasing the amount of NO _2. In doing so, the method according to aspects of the present invention recognizes significantly higher soot regeneration effects and efficiencies than conventional NO ₂ utilization methods by significantly enhancing the benefits of the NO recirculation mechanism over the soot regeneration process.

In aspects of the invention, it is not necessary to maximize the equilibrium-limited NO ₂ supply or to establish a soot oxidation reaction that is approximately balanced between the rate-controlled and diffusion-limited types. Absent. It is not always necessary in the aspect of the present invention to actively expand the engine operating range in which conventional NO ₂ utilization regeneration occurs (by managing heat, volume flow rate, reactant supply). Instead, the concept of “effective NO ₂ supply” is introduced and this effective supply is more effective in removing smoke than the effect expected during conventional NO ₂ utilization regeneration even when the equilibrium limited NO ₂ supply amount is reduced. To be enhanced. Effective NO ₂ supply in this application is defined as the amount of NO ₂ involved in soot oxidation. Participating NO ₂ is determined directly from any of the equilibrium limiting NO ₂ supply, NO oxidized by catalytic DPF, or recirculated NO. The concept of smoke removal capability of NO ₂ reactant is also introduced. Even if the adopted method reduces the equilibrium-limited NO ₂ supply amount, the effective NO ₂ supply amount is also increased at the same time, so that the ability to remove smoke from the equilibrium-limited NO ₂ supply amount is enhanced, resulting in a significant increase High soot oxidation rate is obtained. Even than conventional conditions a small amount of NO ₂ is supplied to the DPF, NO is the speed at which NO ₂ is converted to NO ₂ reacts with soot in the DPF, a large amount of NO ₂ is supplied to the DPF Conditions are controlled to be higher than conventional conditions. In embodiments of the present invention, usually through the catalyst reaction are "recycled" NO is effectively over once to generate NO _2, the NO ₂ reacts with soot, again NO undergoing catalytic reaction Generate. Thus, a certain amount of NOx in the engine exhaust under conditions controlled by aspects of the present invention acts to oxidize a larger amount of soot than the equilibrium limited NO ₂ supply. This aspect of the invention is referred to as “active NO ₂ utilization regeneration (of DPF) with enhanced effective NO ₂ supply”. The amount of effective NO ₂ during conventional active NO ₂ utilization regeneration is mainly for the total allowable NOx amount (determined by the application) and for a given set of operating conditions (including those that are actively controlled). Determined by the equilibrium NO-NO ₂ ratio. In both the application of the concept (method and apparatus) and its effectiveness and efficiency, the significance of the different purposes of the conventional NO ₂ utilization regeneration concept and the concept presented here is important.

O 2 _/ activation energy required to soot reaction is initiated is much higher than those required for NO 2 _/ soot reaction. O 2 _/ for high activation energy required for the soot reaction, at present the catalyst art, the passive O ₂ utilization ability to perform reproduction practical soot in normal operating conditions of the diesel engine has not been demonstrated . Indeed, effective O ₂ utilization regeneration has been actively carried out only at temperatures above about 600 ° C. As such, for those familiar with DPF regeneration, the concept and implementation of “active” regeneration was generally for O ₂ -based regeneration, and the terminology was used interchangeably. Similarly, the concepts and terminology of “passive” regeneration and NO ₂ utilization regeneration have generally been widely used interchangeably, but a distinction should have been made. In the present invention, a method and apparatus for identifying a concept for active “recirculation” NO ₂ utilization regeneration with significantly higher soot removal effect than conventional NO ₂ utilization regeneration and improved overall NOx efficiency is disclosed. establishing a, whereby soot removal effect comparable or greater than this if the active O ₂ based regeneration is not only achieved at a significantly lower exhaust temperature, capturing higher DPF soot than an active O ₂ based regeneration Enables collection and application over a wide operating range. NOx efficiency is due to the mass of NOx (gNOx) delivered to the DPF over a time that is significant to, but not exceeded, the time required to effectively regenerate the substantially full DPF. It shall be clearly defined as the mass of smoke removed (gC). The unit of “gC” is the mass of smoke removed from the DPF, and the unit of “gNOx” is the mass of accumulated NOx feed. The DPF is considered to be substantially full when the DPF soot collection is at least 90% of the soot collection that normally begins to be regenerated in the system under consideration. It is believed that the DPF is effectively regenerated if a significant soot removal rate is not maintained. A significant soot removal rate is determined for the soot removal rate for most of the soot removal. The majority of soot removal is considered to be approximately 50% of the total soot removed.

In contrast to the conventional regeneration concept, the present method and apparatus embodiment provides NO ₂ regeneration using a combination of active thermal management of reactants, specifically thermal management of DPF, and active control of NOx generation. the by actively maximized to enhance the soot removal capacity of the NO ₂ reactants, to allow active manipulation of the volume flow of NO ₂ reactant (therefore residence time). In contrast, conventional NO ₂ utilization regeneration concepts are suitable primarily for the use of catalyst agents and / or less commonly active control of NOx generation to ensure that the entire amount of NO ₂ reactant is suitable for the ambient reactant temperature. Therefore, it is intended to actively extend the operation period in which the conventional regeneration using NO ₂ occurs by increasing the temperature to a certain level or controlling the heat and volume flow rate.

The method and apparatus for active NO ₂ utilization regeneration with enhanced effective NO ₂ supply maximizes the ability of the NO ₂ reactant to remove smoke even when the NO ₂ / NO ratio and hence the equilibrium limiting NO ₂ supply is reduced. The concept is presented and is mainly aimed at this. In practice, this usually means that the NO ₂ / smoke reaction is diffusion-limited, mainly due to the much higher reaction rate kinetic term than in the case of conventional NO ₂ utilization regeneration.

Each C atom trapped in the DPF is involved in an oxidation reaction with one NO ₂ molecule (C + NO ₂ → CO + NO) or an oxidation reaction with two NO ₂ molecules (C + 2NO ₂ → CO ₂ + 2NO). Based on the molar mass of NO ₂ (46.01 g / mol) and C (12.01 g / mol), this reaction stoichiometry indicates that the mass of soot after reaction is ˜13% of the mass of NO ₂ after reaction. (In the case of 1: 2 molar reaction) and 26% (in the case of 1: 1 molar reaction). It is recognized that the particulate matter mainly includes soot, usually empirically represented as C8H, and less importantly unburned HCs and inert materials. Therefore, it is reasonable to estimate that the change in the amount of collected DPF soot during the regeneration process mainly contributes to the removal of C. In the calculations performed here, it is assumed that the change in DPF soot mass contributes only to the removal of C.

For passive regeneration of DPF catalyzed by NO ₂ at normal temperature and residence time ranges within the DPF, the most desirable case is generally a given NO ₂ molecule, or first oxidized to NO ₂ On average, NO molecules would be able to complete less than one soot oxidation reaction before leaving the DPF. This is mainly due to the fact that in conventional operation, high DPF and soot temperatures are generally achieved with short residence times (ie high exhaust mass flow rates and temperatures) where there is no time for NO ₂ to react. Similarly, if the residence time is long (mass flow rate and temperature are low), the DPF and soot temperature rise is not achieved.

The NO ₂ utilization regeneration test introduces a measurement of NO ₂ efficiency related to the reaction stoichiometry of NO ₂ and C to evaluate the effectiveness of a specific method. NO ₂ efficiency is the mass of C removed from the DPF, which is determined over a time that is significant to, but does not exceed, the time required to effectively regenerate a substantially full DPF. Explicitly defined as divided by the mass of NO ₂ provided to the DPF. The DPF is considered to be substantially full when the DPF soot collection is at least 90% of the soot collection that normally begins to be regenerated in the system under consideration. It is believed that the DPF is effectively regenerated if a significant soot removal rate is not maintained. A significant soot removal rate is determined with respect to the soot removal rate in the majority of soot removal. The majority of soot removal is considered to be approximately 50% of the total soot removed.

Calculated based on temporal appearance and / or significant soot removal rate by defining NO ₂ and NOx efficiency over time that is significant relative to the time required to effectively regenerate the DPF It is intended to exclude measurements that represent regeneration that continues beyond the point where is no longer maintained. During the test, a portion of the regenerated soot is supplied from the incoming exhaust, and the associated regeneration reaction does not reduce DPF soot collection. This reduces the measured NO ₂ efficiency along with other factors. Conventional wisdom for conventional NO ₂ based regeneration, the NO ₂ efficiency greatly exceeds _{12.01gC / 46.01gNO 2 = ~0.26gC / gNO} 2 is not. The unit “gC” is the mass of soot removed from the DPF and the unit “gNO ₂ ” is the mass of the accumulated equilibrium limiting NO ₂ feed. Nevertheless, at higher temperatures (near or slightly beyond the flat portion of the NO-NO ₂ conversion as seen in FIG. 2), a gradually decreasing equilibrium-limited NO ₂ feed cannot utilize the temperature rise, It was estimated that the overall NO ₂ utilization soot oxidation activity was significantly reduced. In other words, an increase in temperature simply reduces the amount of NO ₂ supplied, resulting in a more diffusion-limited reaction, thus achieving a reduction in overall smoke removal by reducing the reaction rate. Conventional passive NO ₂ utilization regeneration is well below 0.52 gC / g NO ₂ over a time that is significant but not exceeding the time required to regenerate a substantially full DPF. more generally it has a low NO ₂ efficiently than 0.26gC / gNO _2.

However, in an embodiment of the presented method, can achieve significantly better soot removal results than conventional NO ₂ based regeneration techniques have increased over NO ₂ efficiently 0.52gC / gNO ₂ is active the reaction temperature Only by raising it. This method enables even higher NO ₂ effectively many times than 0.52gC / gNO _2. This is achieved by increasing the NO ₂ soot removal capability for the purpose of enhancing the effective NO ₂ supply (not necessarily the equilibrium limited NO ₂ supply). A mechanism for increasing the NO ₂ soot removal capability is a NO recirculation mechanism. In a catalytic DPF given a sufficiently long residence time and a sufficiently high temperature, NO ₂ molecules that react with the soot and generate NO molecules are recycled to NO ₂ , which is involved in another soot oxidation action The inventors recognize that this is done. The process is repeated as many times as possible due to residence time, kinetic kinetics of the soot oxidation and NO oxidation reactions, soot effectiveness, oxygen effectiveness, and catalyst effectiveness.

It should be noted that the metric “NO ₂ efficiency” is also defined for mole C removed for each mole NO ₂ provided. However, since NO ₂ efficiency is mainly used here as a metric to compare the performance of conventional passive NO ₂ utilization regeneration with active NO ₂ utilization regeneration with enhanced effective NO ₂ supply, gC / gNO Whether expressed in terms of ₂ or in terms of mole C / mole NO ₂ is not considered important at this time. Of course, during conventional passive NO ₂ regeneration, NO recirculation occurs, but the amount of recirculation is achieved through active NO ₂ regeneration with enhanced effective NO ₂ supply. Note that it will be considerably lower than the one.

Furthermore, the NO ₂ efficiency metric is based on the assumption that the catalyst agent is an effective catalyst agent when the catalyst agent is provided upstream of the DPF. Effective catalyst agents are believed to raise the NO ₂ level substantially to the highest equilibrium level possible for the gas conditions of interest. Another assumption is that during conventional passive NO ₂ regeneration, ineffective upstream catalyst agents transmit low levels of NO ₂ , and DPF regeneration is usually a function of NO to NO ₂ conversion in the DPF. However, there is a danger of exhibiting high NO ₂ efficiency without achieving the smoke removal effect according to aspects of the present invention. The models and examples described here assume that the upstream catalyst agent is an effective catalyst agent. For some systems, ie, those that contain an effective upstream catalyst, those that contain an ineffective upstream catalyst, and those that do not contain a catalyst, the equilibrium-restricted NO ₂ supply provides a DPF with no soot. As is the case, it is also considered to refer to the amount of NO ₂ that has passed through the DPF when NO ₂ is not involved in the soot oxidation reaction.

By actively raising the temperature (and as long as possible residence time), the proposed method seeks to maximize the advantages provided by the NO recirculation mechanism. Although some effect is achieved by various methods of extending the dwell time, in conventional drive train mechanisms this is greatly influenced by the engine operating point (speed and load), thus limiting the possibility of shortening the dwell time. The Maximizing the number of NO ₂ molecules is recycled will mainly be achieved by increasing the kinetic term of the NO oxidation reaction by thermal management of the reactants. Number of NO recirculation, since the equilibrium limiting NO ₂ supply amount increases with higher temperature than the drops, the equilibrium limited NO ₂ supply amount effective NO ₂ supplied amount decreases increases.

In practice, the optimum temperature for active NO ₂ utilization regeneration with enhanced effective NO ₂ supply will generally be the highest temperature allowed. This maximum temperature may be a temperature including an uncontrollable O ₂ utilization regeneration that changes from system to system, that is, a temperature including an allowable safety margin from a component temperature limit. However, operating conditions, NO if maximum practical limit for the recirculation is such as is achieved at a given temperature, will reduce the actual effective NO ₂ supplied further temperature increases. The practical maximum limit of NO recirculation is affected by factors such as DPF design and DPF wall physical characteristics. Also note that the method used to raise the DPF temperature affects the regeneration performance. That is, for systems that burn hydrocarbons (HC), including catalytic combustion systems, excess HC slip to the DPF negatively impacts the NO recirculation process. In this case, the regeneration performance is negatively affected under operating conditions in which the HC slip to the DPF increases considerably as a result of the increase in the DPF temperature.

Unless limited by other constraints, the maximum allowable temperature approaches the temperature at which uncontrolled O ₂ utilization regeneration begins, but maintains an appropriate safety margin in the future. The temperature required to operate the uncontrolled O ₂ utilization regeneration decreases as a function of catalyst characteristics and soot density increase. In practice, to ensure that both uncontrolled O ₂ utilization regeneration is not initiated and highly effective active NO ₂ utilization regeneration with enhanced effective NO ₂ supply is achieved, A DPF inlet temperature of about 500 ° C. or less is used. As long as uncontrolled O ₂ utilization regeneration is not initiated, a higher temperature that improves the soot removal result may be used. If necessary, a decrease in soot oxidation performance is observed, but lower temperatures may be used.

Typically, when applying the method according to aspects of the present invention, soot oxidation is maximized when the input NOx flow is optimally increased. Therefore, the constraint imposed on the maximum allowable NOx flow is the soot removal performance, ie, how long it takes to regenerate the DPF from a given start smoke collection amount to a given end smoke collection amount. Decrease or need. However, since the amount of input NOx does not have a significant effect on the NO recirculation mechanism, the decrease in the amount of input NOx does not significantly reduce the NOx efficiency. Conceptually speaking, a decrease in overall NOx flow reduces the effective NO ₂ feed stream, does not decrease the soot removal capacity of the NO ₂ reactants. This means that approximately the same total amount of NOx is required to regenerate a given amount of smoke, and simply requires a long regeneration event. Therefore, the entire amount of NOx required from the engine to regenerate a given soot quantity with aspects of the present invention is significantly less than that required for conventional NO ₂ based regeneration event.

Note that additional energy must be consumed to actively increase the reactant temperature. Therefore, low-cost active NO ₂ utilization regeneration with enhanced effective NO ₂ supply is regeneration that ends with a minimum amount of time (ie, maximum allowable temperature, maximum allowable dwell time, maximum allowable input NOx amount). is there. The regeneration performance of active NO ₂ utilization regeneration with enhanced effective NO ₂ supply is limited in its ability to generate large amounts of NOx due to basic engine constraints such as the highest allowable cylinder pressure. Similarly, the ability to initiate the active NO ₂ based regeneration of the active NO ₂ supply enhancement, such as DOC system requiring a minimum catalyst temperature is limited by actively ability to adjust the reaction temperature.

A NOx aftertreatment device such as an SCR is not required to perform this method, but will allow full or partial reduction of high NOx levels exiting the DPF. NOx generation (along with mass flow manipulation) is achieved through engine control (including injection timing, injection pressure, turbocharger vane position, EGR valve position). Valid NO optimum (or highest allowable) of ₂ supply active NO ₂ in use play in strengthening NOx generation, exhaust gas temperature, and the alternative control strategy devised for DPF residence time, the ECU Executed and started. The aftertreatment hydrocarbon injector injects fuel upstream of the DOC. The injected fuel is oxidized in the DOC to raise the exhaust gas temperature, thereby raising the temperature of the DPF and the trapped soot. Further, the DOC generates NO ₂ supply from the input NOx amount. The amount of NO ₂ generated in the DOC is then sent to the DPF, where soot oxidation is performed according to the method and mechanism described above.

It should be observed that NO ₂ is generated from NO molecules at once in the DOC. However, as illustrated in FIG. 1, NO ₂ may be regenerated from NO molecules several times within the catalytic DPF by the NO recirculation mechanism. In aspects of the present invention, DOC is not required because most of the effective NO ₂ generation occurs in the DPF. Therefore, a system with a catalytic DPF that can further actively adjust the reactant temperature, such as a burner system, an electrical heating system, a microwave system, etc., is used to perform the method. The illustrated system used to describe and describe the concepts and methods is not intended to be representative of all systems in which the methods are implemented.

The current state of the art of catalyst technology allows the regeneration of conventional NO ₂ utilization during a predetermined high exhaust temperature operation period of a diesel engine, but is less effective than that demonstrated for active O ₂ utilization regeneration. Thus, in many applications, relying solely on conventional NO ₂ utilization regeneration is not sufficient to meet the required smoke removal level, and active O ₂ utilization regeneration, active O ₂ utilization and conventional NO ₂ utilization. One of the combinations with use reproduction is adopted. However, due to the nature of the O ₂ / smoke reaction where the exotherm and reaction rate are controlled, constraints are needed to avoid uncontrolled O ₂ utilization regeneration. That is, the requirements of minimum exhaust mass flow rate and maximum allowable DPF soot collection must be maintained. The minimum exhaust mass flow restriction increases the likelihood that incomplete regeneration will occur when actually performed. The maximum DPF soot collection will determine how often DPF regeneration is required.

Due to the diffusion limiting nature of the active NO ₂ utilization regeneration method with enhanced effective NO ₂ supply, an uncontrollable NO ₂ soot oxidation reaction does not occur. According to the aspect of the present invention, it is possible to start non-controlled O ₂ utilization regeneration. However, the exhaust mass flow constraints are reduced by aspects of the method and apparatus for active NO ₂ utilization regeneration with enhanced effective NO ₂ supply. Similarly, aspects of the present invention significantly increase the DPF soot density required to initiate uncontrolled O ₂ utilization regeneration. Due to the high acceptable DPF soot collection level, regeneration is not required too often. In certain applications, the acceptable DPF soot collection level is high, resulting in an equilibrium soot collection level that is lower than the highest DPF soot collection level but higher than that possible with an O ₂ utilizing regeneration system. Thus, active regeneration is not necessary for these applications in normal situations. However, even if DPF collection continues to rise beyond the expected equilibrium due to abnormal work, component failure, or other causes, active NO ₂ regeneration with enhanced effective NO ₂ supply will provide O ₂ recovery. Safe playback that is not possible with use playback is possible.

Furthermore, effective NO ₂ supplied reinforcing active NO ₂ based regeneration of may achieve a temperature much lower than the O ₂ based regeneration with equivalent effect, thereby negatively performance impact and failure to the associated exhaust post-treatment device Reduce the possibility of This would include downstream components of the soot filtration regeneration system, such as the SCR.

FIG. 3A graphically illustrates an example of conventional NO ₂ utilization regeneration and an example of active NO ₂ regeneration with enhanced effective NO ₂ supply. Examples 1 and 2 show regeneration results using the conventional NO ₂ method, while Examples 3A and 3B show regeneration results using aspects of the present invention. The total event time for regeneration shown graphically in FIG. 3A is shown in the table of FIG. 3B. The total event time for these regenerations includes the time spent warming up the test system, so the NOx and NO ₂ efficiencies shown in Table 1 below are the time periods after normal regeneration conditions are reached. perhaps slightly lower than when the amount of NOx and NO ₂ were measured for only. However, if the warm-up period is not included, the difference between the conventional NO ₂ utilization regeneration of Examples 1 and 2 and the active NO ₂ utilization regeneration of enhanced effective NO ₂ supply of Examples 3A and 3B is even more dramatic. It is expected to be preferable.

  All of the tests described in Examples 1, 2, 3A and 3B were performed with an engine dynamometer and the engine operated at the same engine speed and brake torque. The same equipment was used for each test. The engine was a US2010 Volvo MD11L B-Phase large diesel engine, and the exhaust aftertreatment system was a Fretguard B-Phase DOC and DPF for Volvo US2010 MD11. DOC and DPF contained a noble metal oxidation catalyst and the heating mechanism used was HC injection into the DOC.

  The test method was performed as follows for measuring the amount of smoke collected. The engine was operated in a predetermined soot collection routine for collecting with DPF. To avoid errors due to moisture absorption, the DPF was weighed at a high temperature and the starting smoke collection was calculated. The DPF was installed again and the desired regeneration method was implemented over the measurement time length. Immediately after regeneration, the high temperature weight was recorded, a new amount of smoke collected was calculated, and changes in the amount of smoke collected were judged. At this point, one or two additional regenerations were performed for Examples 1 and 2, respectively, and a new amount of smoke collected after each regeneration was measured. When the desired number of regenerations were completed, the DPF was regenerated over an extended period of time using a highly effective method.

Table 1 shows a summary of key statistics four examples, i.e. removed soot mass, the stored NOx and NO _2, calculated NOx and NO ₂ efficiency, fuel consumption total. To determine the amount of accumulated NOx and NO ₂ is used in NOx and NO ₂ efficiency calculation, the sum of NOx and NO ₂ in the DPF inlet was sought. In order to determine the accumulated NO ₂ , a model of DOC's NO ₂ conversion efficiency was created for all examples to determine the percentage of NO ₂ to NO x, referred to herein as NO ₂ percent. In addition, in tests where the conditions of Examples 3A and 3B were repeated, NO ₂ was measured to confirm the unexpected results achieved in Examples 3A and 3B.

  In Examples 1 and 2, the engine was calibrated to increase NOx generation and to raise the exhaust gas temperature as much as possible without the aid of HC injection. There is a trade-off between NOx generation and exhaust gas temperature. In Example 1, a trade-off was made for a higher exhaust gas temperature, whereas in Example 2 a bias was applied for a higher NOx mass flow. The resulting DPF inlet temperatures for Examples 1 and 2 were in the range of approximately 350-390 ° C, and the average DPF temperature was approximately 325-375 ° C.

These average DPF temperature during typical operation in at least a portion of the duty cycle, closer to those found in a typical passive NO ₂ based regeneration. In order to conduct a steady state test that is easier to analyze, it is considered to be an example that represents a reasonable comparison between a conventional method and active NO ₂ utilization regeneration with enhanced effective NO ₂ supply.

Examples 3A and 3B show that active NO ₂ utilization regeneration with enhanced effective NO ₂ supply was performed at two different regeneration times. In Examples 3A and 3B, the engine was calibrated to further increase NOx over Example 2. In addition, HC injection to the DOC was used to control the DPF inlet temperature to approximately 490 ° C, resulting in an average DPF temperature of approximately 470 ° C. Regeneration (examples 1 and 2) by what is referred to herein as prior art tends to take more time than active NO ₂ utilization regeneration with enhanced effective NO ₂ supply (examples 3A and 3B). , 3A, 3B. Further, NOx efficiency and the NO ₂ efficiency of active NO ₂ based regeneration of the active NO ₂ supplied reinforcing tends to considerably higher than NOx efficiency and the NO ₂ efficiency of the conventional art.

  A particularly useful exhaust aftertreatment system (EATS) 21 with respect to the diesel engine 23 is shown in FIG. The EATS 21 includes a diesel particulate filter (DPF) 25 downstream of the diesel engine 23. The DPF 25 is configured to receive an exhaust gas flow from the engine 23.

In order to implement active NO ₂ utilization regeneration with enhanced effective NO ₂ supply, the diesel engine configuration includes a diesel engine 23 configured to introduce NOx-containing gas into the catalytic DPF 25. The mass flow rate of the NOx-containing gas may be controlled by an appropriate method such as variable valve timing, cylinder operation stop, or use of a drive system mechanism different from the conventional one. In an active NO ₂ based regeneration of the active NO ₂ supply reinforced, usually, by adjusting the local flame temperature in the upstream of the engine cylinders of DPF, NOx levels at the inlet of the DPF25 is controlled. Further, the heating mechanism 47 is configured to control the temperature of at least one of the DPF 25, the NOx-containing gas, and / or the smoke in the DPF. NOx-containing gas reacts with the catalyst to generate NO ₂ molecules to generate then react with soot particles CO, _CO 2, NO molecules higher than 0.52gC / gNO _2, more preferably about 1 by controlling the temperature so as to achieve a high NO ₂ efficiently than .04gC / gNO _2, by controlling the heating mechanism, to assist the active NO ₂ based regeneration of the active NO ₂ supply reinforced, the controller 53 Is configured.

The heating mechanism 47 includes a hydrocarbon injection mechanism configured to control the temperature of at least one of the DPF 25 and the NOx-containing gas by injecting hydrocarbons into the diesel engine exhaust stream upstream of the DPF. The heating mechanism includes a catalyst such as DPF 25 or DOC 43 upstream of the DPF to react with hydrocarbons to increase the exhaust gas temperature and / or to facilitate the conversion of NO to NO ₂ . The heating mechanism 47 includes a burner for burning hydrocarbons. The heating mechanism 47 may be of a type that heats the DPF 25 instead of the NOx-containing gas flow, such as an electric heating mechanism or a microwave mechanism for heating the smoke.

A conduit 29 is provided to allow recirculation of gas containing NO and / or NO ₂ or both, usually recirculated from point 31 downstream of DPF 25 to point 33 normally upstream of DPF. . NO and / or NO ₂ is recirculated during passive or active conventional NO ₂ utilization regeneration and O ₂ utilization regeneration, as well as during active NO ₂ utilization regeneration with enhanced effective NO ₂ supply. It is beneficial to let The expressions “downstream of DPF” and “upstream of DPF” for DPF 25 refer to points on the DPF that are downstream or upstream of a substantial portion of the DPF, that is, the conduit 29 reaches the first point downstream of the DPF inlet. It is intended to include configurations where points 31 and 33 are spaced from the DPF, as well as configurations where the conduit connects directly to one or more points on the DPF to connect to another point downstream of one point. An oxidation catalyst such as DOC is provided upstream (DOC43) or downstream (DOC2 43 ′) of the DPF, and recirculated from a point between the upstream oxidation catalyst inlet and the DPF outlet to a point upstream of the branch point. Other configurations are possible, such as If the recirculation branch is from the oxidation catalyst DOC2 43 ′ downstream of the DPF, the recirculation is to a point upstream of the DPF outlet. In theory, such that at least a portion of NOx _(and / or both NO, to generate NO 2, _{O 2} reacts with NO ₂₎ is recycled, an oxidation catalyst (if provided) or DPF The recirculation may be performed from the branch point downstream of the entrance to the point upstream of the branch point.

The reaction zone may be configured to react the recycled NO with O ₂ to produce NO ₂ . The reaction region includes a region 37 that includes a point 35 where air or O ₂ (hereinafter referred to as “air / O ₂ ”) is injected and mixed with recirculated NO to produce NO ₂ . The reaction region may additionally or alternatively include regions recirculation NO to generate NO ₂ reacts with O ₂ in the presence of a catalyst. The region where the recycled NO reacts with O _{2 in} the presence of the catalyst is the region 39 where the catalyst is in the DPF, but the region where the recycled NO reacts with O _{2 in} the presence of the catalyst is the diesel upstream of the DPF. This is a region 41 where the catalyst includes an oxidation catalyst (DOC) 43. The reaction zone includes, in addition to one or more of the reaction zones 37, 39, 41, other zones in which NO reacts with O _2, and the purpose of providing these zones is simply the NO and O ₂ . reaction to promote and to generate NO _2.

Air / O ₂ is injected downstream of the DPF 25 and upstream of the downstream DOC2 43 ′. This is useful, for example, in facilitating the conversion of NO to NO ₂ in DOC2 43 ′ so that NO ₂ is recycled to DPF 25. For the purpose of enhancing regeneration, air / O ₂ may be injected at some point in the exhaust aftertreatment system.

NO ₂ is recirculated, or NO ₂ is generated from the recirculated NO and then NO ₂ is used to oxidize the soot to produce CO, CO ₂ , NO and then recycle NO to NO ₂ at least further The regeneration of the DPF 25 by terminating one smoke oxidation reaction is referred to as “active NO ₂ utilization regeneration (for DPF) with enhanced effective NO ₂ supply using recirculated NOx”. The method of recirculating NOx not only enhances the regeneration effect, but also does this without increasing the NOx exiting the system after adjustment. It is conceivable that both NO recirculation and NOx recirculation in this DPF are effectively used together, such as to increase the NO residence time in the catalytic DPF. (Must include catalyzed DPF, it is not necessary with the NOx recirculation) active NO ₂ based regeneration of the active NO ₂ supplied reinforcing accompanied with the NO ₂ based regeneration (catalyzed DPF with recirculation NOx Both are in contrast to traditional NO ₂ utilization regeneration which seeks to approach the equilibrium point between reaction rate limitation and diffusion limitation. Enable NO ₂ and supply an active NO ₂ based regeneration of reinforcement, both of NO ₂ based regeneration using recirculated NOx is also substantially all of the soot is removed by reaction with _{O 2,} the conventional NO ₂ Use reproduction, active nO ₂ use of effective nO ₂ supplied reinforcing playback, or rather high temperatures (about 600 ° C. to about 625 ° C. for catalysis DPF than nO ₂ based regeneration using recirculated NOx, for no catalytic DPF In contrast to the active O ₂ utilization regeneration commonly performed at 660 ° C. and sometimes above 660 ° C.). Active O ₂ utilization regeneration also generally involves heating the exhaust stream at the DPF inlet 45, such as a heating mechanism 47 such as a post-treatment hydrocarbon injector.

In order to reduce NOx emissions, a NOx aftertreatment device such as a selective catalytic reduction aftertreatment device (SCR) 49 may be provided downstream of the DPF 25. The reaction region 37 into which air / O ₂ is injected may be arranged downstream of the DPF 25 and upstream of the SCR 49, but is usually arranged upstream of the DPF and, if provided, the DOC 43. However, in some situations it may be beneficial to inject air / O ₂ downstream of the DPF 25. Alternatively, the air / O ₂ injection point 35 may be downstream of the DOC 43 (if provided). For NO ₂ utilization regeneration using recirculated NOx, conduit 29 is such that the gas recirculated through the conduit includes at least a portion of the injected air / O ₂ that reacts with the recirculated NO to produce NO _2. More specifically, a conduit point 31 downstream of the DPF 25 may be located downstream of the region 51 where air / O ₂ is injected.

A temperature monitor 52 is provided and is associated with a controller 53 such as one or more ECUs including one or more computers or microprocessors for controlling the temperature of the DPF 25 or DPF inlet 45. The temperature monitor 52 is usually disposed at the inlet 45 of the DPF 25 or upstream thereof. Typically, the temperature during active NO ₂ utilization regeneration with enhanced effective NO ₂ supply is maintained below about 550 ° C. or below about 500 ° C., and usually at a minimum of 450 ° C. When the temperature is expressed as “about” how many times or less, it goes without saying that the temperature may exceed the specific value by a small amount, and it may temporarily appear that the temperature exceeds the specific value by a small amount or more. The heating mechanism 47 is controlled by the controller 53 in order to raise the temperature to a desired temperature range. If the temperature exceeds the desired range, appropriate cooling means may be taken, such as introducing external air / O ₂ into the injection region 37 by controlling the valve 55 via the controller 53. The controller 53 controls the valve 56 in the air / O ₂ line 51 (if provided) downstream of the DPF 25 to control the temperature of the SCR 49 or to control the mixing of recirculation NO and O _2. Also good.

While the above temperature range approaches about 550 ° C. or higher, there is usually a high risk of uncontrollable regeneration with a DPF having a large amount of smoke collection. At temperatures below about 550 ° C., theoretically, less than two-thirds and possibly less than half of the smoke removed is removed by reaction with O ₂ during active NO ₂ regeneration with enhanced effective NO ₂ supply. The Evaluation of the theoretical percentage of soot mass that is removed from the DPF by oxidation with O ₂ molecules in the gas to produce CO and CO ₂ molecules (also represented by the abbreviated term “O ₂ involvement” in soot removal) Must be done for a time that is significant but not exceeding the length of effective regeneration of the substantially full DPF. If significant smoke removal rate is not maintained, the DPF is considered to have been effectively regenerated. A significant soot removal rate is determined for the soot removal rate in most of the soot removal. The majority of soot removal is considered to be approximately 50% of the total soot removed. A DPF is considered substantially full when the DPF soot collection is typically at least 90% of the soot collection that begins to be regenerated in the system under consideration. It is now recognized that for various reasons, there is a theoretical tendency to suggest higher O ₂ involvement than it actually occurs.

At temperatures below about 550 ° C., substantially all soot removal is O ₂ if the NOx level at the DPF inlet is not controlled to occur during active NO ₂ utilization regeneration with enhanced effective NO ₂ supply. Slow regeneration, which is due to the reaction with Control and Control of NOx level of the temperature through the active NO ₂ based regeneration of the active NO ₂ supply enhancement is usually substantially increases the regeneration effect.

Usually, when the temperature rises enough that more than two-thirds of the smoke removed is removed by reaction with O ₂ , this temperature is typically the low temperature of some O ₂ utilization regeneration. Although approaching the temperature associated with the range, in this O ₂ regeneration, in theory NOx is not controlled as in the active NO ₂ regeneration with enhanced effective NO ₂ supply, so virtually all soot removal is Performed with O ₂ . Enable NO ₂ with active NO ₂ Use NOx levels at the inlet of the DPF as regeneration of supply reinforced is controlled, sufficient to more than two-thirds of the soot removed is removed by reaction with O ₂ If the temperature rises so much, there is a risk of uncontrolled regeneration in a DPF that collects a large amount of smoke.

To produce CO and CO ₂ molecules by oxidation i.e. O ₂ involved by O ₂ molecules in the gas, the percentage of soot mass that is removed from the DPF in some way, such as during the active NO ₂ based regeneration of the active NO ₂ supplied strengthen A useful but not necessarily limiting technique for judging involves a series of empirical tests, i.e., a series of empirical regenerations, and is significant for the time required to effectively regenerate the DPF. Each regeneration took place over the same time that never exceeded. If the significant smoke removal rate is not maintained, the DPF shall be deemed to have been regenerated effectively. A significant soot removal rate is determined with respect to the soot removal rate in the majority of soot removal. The majority of soot removal is considered to be approximately 50% of the total soot removed.

The technique devised to determine the O ₂ participation proceeds as follows.
(A) The DPF is effectively cleaned. Various suitable methods for cleaning the DPF are well known, and the particular method used to clean the DPF must yield a fairly consistent result, and the same method is consistently consistent. It is not considered particularly important except that it should be used.
(B) Subsequent to step (A), the DPF normally collects up to at least 90% of the amount of soot collected at the system under consideration. Specific conditions and methods for collecting with DPF should yield fairly consistent results, and the same conditions and methods should be used consistently.
(C) Subsequent to step (B), NO ₂ utilization regeneration for strengthening effective NO ₂ supply, etc. over a time that is significant but does not exceed the time required to effectively regenerate the DPF The DPF is regenerated by the method to be investigated (“Investigative regeneration”). The total smoke removal during regeneration is measured.
(D) Following step (C), the DPF is effectively cleaned again.
(E) Subsequent to step (D), collection is performed with DPF up to the same starting smoke collection amount as in the exploratory regeneration (or close to a reasonable collection amount).
(F) Following step (E), the DPF is regenerated by a relative regeneration method (“relative regeneration”) for a time equal to the time of exploratory regeneration. Relative regeneration is performed in the same manner as exploratory regeneration, except that the NOx level at the DPF inlet has dropped to a level that is significant for DPF regeneration. At the end of the relative regeneration, the total soot removal is measured.
(G) The total soot removal by relative regeneration is divided by the soot removal total of the exploratory regeneration and removed from the DPF by oxidation with O ₂ molecules in the gas during the exploratory regeneration to produce CO and CO ₂ molecules. The maximum fraction of soot mass is determined.

Points that are calculated on the basis of temporal appearance by defining O ₂ participation in a time that is significant relative to the time required for effective regeneration and / or a significant soot removal rate is no longer maintained It is intended to exclude measurements that represent replay that continues beyond.

The technique described here is expected to overestimate the actual fraction of the soot mass removed by O ₂ during exploratory regeneration, and is therefore the conventional standard for O ₂ involvement. More accurate empirical and / or theoretical techniques may show even lower O ₂ participation levels than would be expected to be demonstrated by the methods described above.

The controller 53 also stops or initiates NO ₂ utilization regeneration using recirculated NOx in which at least a portion of the soot is oxidized by NO ₂ generated from or carried by the recirculated gas, When regeneration using NO ₂ using recirculated NOx is stopped, soot is oxidized without recirculation, so that a regeneration operation by regenerating active NO ₂ using conventional or enhanced NO ₂ supply is generated. It is also configured to start and stop NOx recirculation in the conduit, such as by opening and closing the valve 57 of the conduit 29. NO ₂ based regeneration using recirculated NOx is completely stopped, to operate in some aborted, or maximum capacity, the valve 57 of the conduit 29 is typically in addition to a plurality of positions including a fully open and fully closed, fully open And can be adjusted to a position between fully closed. Control of NOx generation from the engine 23 and / or control of the regeneration rate of the DPF can be facilitated if the regeneration using NO ₂ can be adjusted using the recirculated NOx.

Controller 53 controls the heating mechanism 47, when the effective NO ₂ supplied strengthening active NO ₂ based regeneration or recycling NOx NO ₂ based regeneration using was discontinued at least partially, the inlet of the DPF 25 45 An active O ₂ utilization regeneration operation is also initiated in which the temperature at the temperature rises sufficiently to oxidize the soot in the DPF with O ₂ in the exhaust stream. When the soot collection level is low enough, this method is at least partially discontinued by increasing the temperature of the DPF inlet 45, increasing the temperature of the DPF 25, increasing the temperature of the soot, etc. O ₂ utilization regeneration is started.

The pressure sensor mechanism 59 has a configuration related to the DPF 25 and is suitable for sending a signal corresponding to a pressure drop in the DPF to the control device 53. The pressure drop in the DPF 25 is often related to the amount of smoke collected by the DPF (along with the volume flow in the DPF). Various playback methods with various playback methods may be implemented. For example, a regeneration scheme may be devised to implement various regeneration methods depending on the pressure drop in the DPF 25 or otherwise indicating smoke collection. At high soot collection levels, the temperature associated with O ₂ utilization regeneration is generally high enough to cause uncontrollable regeneration that can damage the DPF. The low temperature for O ₂ regeneration, generally associated with active NO ₂ regeneration with enhanced effective NO ₂ supply, still causes uncontrolled O ₂ regeneration reactions that damage the DPF when the smoke collection level is still high. High enough to get you started. In such a high soot collection levels, conventional NO ₂ based regeneration, i.e. from the start of the reproducing system with NO ₂ based regeneration with low NO ₂ efficiently than 0.52gC / gNO _2, pressure drop in the DPF 25 (or After the other soot collection level shows a low soot collection level, it switches to active NO ₂ regeneration with enhanced effective NO ₂ supply. When the displayed amount of smoke collected further decreases, active O ₂ utilization regeneration is started. Conventional NO ₂ based regeneration, effective NO ₂ supplied active NO ₂ Use of reinforced regeneration, in either an active _{O 2} based regeneration, the NO ₂ based regeneration using recirculated NOx (NO and / or NO ₂ again (With circulation) can be performed simultaneously. Also, if the conventional NO ₂ based regeneration, an active NO ₂ based regeneration of the active NO ₂ supply reinforced, in either an active _{O 2} based regeneration, the regenerated using recirculation NOx is switched to NO ₂ based regeneration The reverse is done.

Usually, by adjusting the local flame temperature upstream of the engine cylinders of DPF, the speed of conventional, and / or active NO ₂ based regeneration of the active NO ₂ supplied strengthening, and / or NOx generated from the engine 23 The controller 53 is also configured to adjust the NOx level of the exhaust gas flow for the purpose of adjusting the exhaust gas flow. This is further controlled by the controller 53 by appropriate adjustment of one or more of the fuel injection timing and / or fuel injection pressure of the fuel injection system 61, the vane position of the turbocharger 63, and the position of the EGR valve 65, for example. This is achieved by other actuators such as throttles. In this way, the conventional NO ₂ based regeneration, effective NO ₂ supplied strengthening active NO ₂ based regeneration, in addition to the available NOx to NO ₂ based regeneration using recirculated NOx, NOx emissions from EATS21 Is adjusted. In general, in active NO ₂ utilization regeneration with enhanced effective NO ₂ supply, the NOx level at the inlet of the DPF, which is a level generally defined by environment-related laws, is made higher than the level that the gas normally has. This is controlled. The degree to which the NOx level is controlled generally depends on factors such as the specific NOx source, such as different sized diesel engines, and other operating conditions, and varies greatly from system to system.

  Venturi effect resulting from mechanical flow 67 (represented by dotted lines) for recirculating gas in conduit 29, such as by providing a pump in the conduit, or resulting from gas flow through exhaust line 69 upstream of the DPF, for example The gas is recirculated.

In the method for regenerating DPF 25 according to aspects of the present invention, soot in catalytic DPF 25 is oxidized with NO ₂ so that CO, CO ₂ , NO is produced. According to this method, the NOx-containing gas is introduced into the catalytic DPF 25, and the temperature of at least one of the DPF, the trapped soot and the NOx-containing gas is controlled by the heating mechanism 47, etc., and the NOx-containing gas reacts with the catalyst. later react with soot particles CO, generates a NO ₂ molecules to generate a _CO 2, NO molecules, as NO ₂ efficiency is higher than 0.52gC / gNO _2, and soot mass that is removed from the DPF The NOx level at the DPF inlet is controlled so that less than two-thirds of this is oxidized by O ₂ molecules in the gas to produce CO and CO ₂ molecules.

  The temperature of at least one of the DPF 25, trapped soot, NOx containing gas is typically controlled such that this temperature is less than about 550 ° C, less than about 500 ° C, and at least 450 degrees. NOx from downstream of the DPF 25 is recirculated upstream of the DPF, usually upstream of the diesel oxidation catalyst (DOC) 43 upstream of the provided DPF. The temperature at the inlet of the DOC 43 is controlled, such as by injecting hydrocarbons into the diesel engine exhaust stream upstream of the DOC.

Various measures are taken to adjust the composition of the NOx-containing gas flowing into the DPF. Air / O ₂ is injected upstream of the DPF. The NOx generation of the diesel engine upstream of the DPF is adjusted, such as by adjusting the local flame temperature of the engine cylinder upstream of the DPF.

By generating NO ₂ recirculation NO by reaction with _{O 2} at least partially recirculate and one or more reaction zones 37, 39, and / or 41 of NO from DPF, recirculation NOx The regeneration using the NO _{2 of} the DPF 25 using is performed. Between NO ₂ based regeneration using recirculated NOx, at least part of the NO ₂ which is oxidized soot in DPF25 is NO _2, which is carried by this or are produced from the recycle gas. Inlet temperature 45 DPF25 is normally to exceed at least 450 ° C. This temperature is from about 500 ° C., the active NO ₂ based regeneration and re-effective NO ₂ supplied enhanced when implemented using a catalyzed DPF Control is performed during NO ₂ utilization regeneration using circulating NOx.

During NO ₂ regeneration using recirculated NOx, NOx from the point 31 downstream of the DPF 25 is recirculated to the point 33 upstream of the DPF. Air / O ₂ is injected upstream of the DPF 25 during active regeneration, such as in a reaction zone 37 where O ₂ reacts with recirculated NO to produce recirculated NO ₂ . Additionally or alternatively, recycled NO reacts with O _{2 in} the presence of the catalyst during active regeneration, such as in reaction region 41 of DOC 43 and / or reaction region 39 of catalytic DPF 25.

The NOx gas that leaves the DPF 25 and is not recirculated is processed by the SCR 49 downstream of the DPF to reduce the NOx level. Air / O ₂ is injected to a point 51 downstream of the DPF and upstream of the SCR, and a part of the injected air / O ₂ is recirculated together with the recirculated NOx to regenerate NO ₂ using the recirculated NOx. Promotes the production of NO ₂ for use. The injected air / O ₂ is also used to control the temperature at the inlet of the SCR 49.

Generation of NOx is controlled by the control device 53 and the like in the diesel engine 23 upstream of the DPF 25 by controlling the local flame temperature of the cylinder of the engine. This is achieved, for example, by adjusting the fuel injection timing and pressure of the fuel injection system 61, the vane position of the turbocharger 63, and the position of the EGR valve 65. In this way, the conventional NO ₂ based regeneration, or effective NO ₂ supplied active NO ₂ based regeneration of reinforced or recycling NOx effective NOx to NO ₂ based regeneration using, together with NOx emissions from EATS21 Adjusted.

Based on some characteristic indicating the soot collection level in the DPF or the pressure drop in the DPF 25, the active O ₂ utilization regeneration is started by the controller 53 or the like. Further, the NO ₂ regeneration using the recirculated NOx is terminated by closing the valve 57 of the conduit 29 and the like, and the active O ₂ regenerating including the oxidation of the smoke without the recirculated NO ₂ or the conventional NO ₂ utilization. Regeneration or active NO ₂ utilization regeneration with enhanced effective NO ₂ supply is performed. In this way, the regeneration rate of DPF and / or NOx emissions from EATS 21 are adjusted.

  In this application, the use of “including” is non-limiting and has the same meaning as a word such as “comprising” but excludes the presence of other structures, materials, or actions. It is not a thing. Similarly, the use of the word “can” or “may” is intended to indicate that it is non-limiting and that its structure, material, or action is not required, but without using such a word. There is no intent to show that structure, material, and action are essential. As long as this structure, material, and action are considered essential at this time, it is clearly stated.

  While the invention has been illustrated and described in accordance with preferred embodiments, it will be understood that variations and modifications can be effected without departing from the invention as set forth in the claims.

10 Catalyst 11 Diesel particulate filter 12 Smoke 21 EATS (Exhaust aftertreatment system)
23 Diesel engine 25 DPF (Diesel particulate filter)
29 Conduit 31 Branch point 33 Discharge point 35 Injection point 37 Injection region 39, 41 Reaction region 43 DOC (diesel oxidation catalyst)
43 'DOC2 (diesel oxidation catalyst 2)
45 inlet 47 heating mechanism 49 SCR (selective catalytic reduction aftertreatment device)
51 Air / O ₂ Line 52 Temperature Monitor 53 Controller 55, 56, 57 Valve 59 Pressure Sensor Mechanism 61 Fuel Injection System 63 Turbocharger 65 EGR Valve 67 Mechanical Means 69 Exhaust Line

Claims (34)

A method for regenerating a catalytic diesel particulate filter (DPF) by active NO ₂ utilization regeneration with enhanced effective NO ₂ supply comprising:
Introducing NOx-containing gas into the DPF;
At least an engine comprising adjusting fuel injection timing and pressure, a turbocharger vane position and an EGR valve position of a fuel injection system located upstream of the DPF so as to control a NOx level at an inlet of the DPF By controlling the temperature of at least one of the DPF, the NOx-containing gas, and the smoke in the DPF with a heating mechanism while operating,
First of NO ₂ molecules contained in the NOx-containing gas, and NO ₂ molecules produced from the NO molecules contained in the NOx-containing gas, to produce a CO, _CO 2, NO molecules react with soot particles Carrying out the reaction;
Performing at least one series of second reactions, NO molecules generated in at least one of the first reaction and one reaction in the series of second reactions, and O ₂ molecules in the DPF; Further reacting with the catalyst to at least partially produce NO ₂ molecules that subsequently react with the soot particles,
Thereby, NO ₂ efficiency is higher than 0.52gC / gNO _2, and generates a _O is oxidized by ₂ molecules CO and CO ₂ molecules of less than 2 in the gas-thirds of the soot mass that is removed from the DPF how to. While controlling the NOx level at the inlet of the DPF such that less than half of the smoke mass removed from the DPF is oxidized by O ₂ molecules in the gas to produce CO and CO ₂ molecules, the DPF The method of claim 1, comprising controlling a temperature of at least one of the NOx-containing gas and soot in the DPF.   The method of claim 1, comprising controlling the temperature such that the temperature of at least one of the DPF, the trapped soot, and the NOx-containing gas is about 550 ° C. or less.   The method of claim 1, comprising controlling the temperature so that at least one of the DPF, the trapped smoke, and the NOx-containing gas has a temperature of about 500 ° C. or less.   The method of claim 1, comprising controlling the temperature such that the temperature of at least one of the DPF, the trapped soot, and the NOx-containing gas is greater than about 450 ° C.   The method of claim 1, comprising recycling NO from downstream of the DPF to upstream of the DPF.   The method of claim 6, comprising recycling NO upstream of a diesel oxidation catalyst (DOC) upstream of the DPF.   8. The method of claim 7, comprising controlling the temperature at the DOC inlet by injecting hydrocarbons into a diesel engine exhaust stream upstream of the DOC. The method of claim 1, comprising injecting O ₂ upstream of the DPF.   The method of claim 1, comprising controlling the NOx level at the inlet of the DPF by controlling NOx generation in a diesel engine upstream of the DPF.   The method of claim 1, comprising adjusting a local flame temperature in an engine cylinder upstream of the DPF to adjust NOx generation.   The method of claim 1, comprising controlling the temperature of at least one of the DPF and the NOx-containing gas by injecting hydrocarbons into a diesel engine exhaust stream upstream of the DPF.   13. The method of claim 12, comprising oxidizing the hydrocarbon in the presence of a catalyst.   The method of claim 12, comprising oxidizing the hydrocarbon in a burner system.   The method of claim 1, comprising controlling a temperature of at least one of the DPF and the NOx-containing gas by heating the DPF.   The method of claim 1, comprising heating the DPF with an electric heater.   The method of claim 1, comprising heating the soot with microwaves. The NO ₂ efficiency is higher than 1.04gC / gNO _2, The method of claim 1.   The method of claim 1, comprising controlling a mass flow rate of the NOx-containing gas. A diesel engine configured to introduce NOx-containing gas into a catalytic diesel particulate filter (DPF);
A heating mechanism configured to control the temperature of at least one of the DPF, the NOx-containing gas, and the smoke of the DPF;
First of NO ₂ molecules contained in the NOx-containing gas, and NO ₂ molecules produced from the NO molecules contained in the NOx-containing gas, to produce a CO, _CO 2, NO molecules react with soot particles While carrying out the reaction,
Performing at least one series of second reactions, NO molecules generated in at least one of the first reaction and one reaction in the series of second reactions, and O ₂ molecules in the DPF; Is further reacted with the catalyst to at least partially generate NO ₂ molecules that subsequently react with the soot particles,
As NO ₂ efficiency is higher than 0.52gC / gNO _2, and less than two thirds of the soot mass that is removed from the DPF is a is with CO and CO ₂ molecules oxidized by _{O 2} molecules in the gas At least engine operation including controlling the temperature to produce and adjusting fuel injection timing and pressure of a fuel injection system located upstream of the DPF, a vane position of a turbocharger and a position of an EGR valve A control device configured to control the heating mechanism that performs active NO ₂ utilization regeneration in which effective NO ₂ supply is enhanced by controlling the NOx level at the inlet of the DPF while
Including diesel engine mechanism.   The heating mechanism includes a hydrocarbon injection mechanism configured to control the temperature of at least one of the DPF and the NOx-containing gas by injecting hydrocarbons into a diesel engine exhaust stream upstream of the DPF. The diesel engine mechanism according to claim 20.   The diesel engine mechanism of claim 21, comprising a catalyst for oxidizing the hydrocarbon.   The diesel engine mechanism of claim 21 including a burner for oxidizing the hydrocarbon.   The diesel engine mechanism according to claim 20, comprising a heating mechanism for heating the DPF.   The diesel engine mechanism according to claim 20, wherein the heating mechanism includes an electric heater for heating the DPF.   The diesel engine mechanism according to claim 20, wherein the heating mechanism includes a microwave mechanism for heating the smoke. A method for regenerating a diesel particulate filter (DPF) comprising:
Introducing a NOx-containing gas into the DPF;
First of NO ₂ molecules contained in the NOx-containing gas, and NO ₂ molecules produced from the NO molecules contained in the NOx-containing gas, to produce a CO, _CO 2, NO molecules react with soot particles Performing a reaction, performing at least one series of second reactions, and generating NO molecules generated in at least one of the first reaction and one of the series of second reactions, and in the DPF of _{O 2} molecules and are further reacted with the catalyst, said NO ₂ molecules react with soot particles at least partially generated after, as NO ₂ efficiency is higher than 0.52gC / gNO _2, the CO 2 less than 3 minutes of the soot mass that is removed from the DPF is oxidized by O ₂ molecules in the gas, so as to produce a CO ₂ molecule, so as to control the NOx level of the inlet of the DPF Adjusting the DPF, the NOx-containing gas, and at least operating the engine, including adjusting the fuel injection timing and pressure of the fuel injection system located upstream of the DPF, the vane position of the turbocharger, and the position of the EGR valve. By performing active NO ₂ utilization regeneration that enhances the effective NO ₂ supply, including operating a heating mechanism to control the temperature of at least one of the DPF soot, the DPF is at least partially Performing a first reproduction to reproduce; and
Performing a _second regeneration that at least partially regenerates the DPF by performing at least one of passive NO ₂ regeneration and active O ₂ regeneration;
Including the method.   28. The method of claim 27, wherein the first regeneration is performed before the second regeneration.   28. The method of claim 27, wherein the first regeneration is performed after the second regeneration. After regeneration to at least partially regenerate the DPF by performing the regeneration using passive NO ₂ and before regeneration to at least partially regenerate the DPF by performing regeneration using the active O ₂ 28. The method of claim 27, wherein the first regeneration is performed. It encompasses active NO ₂ Use performing a regeneration of the active NO ₂ supplied reinforced with recirculation NOx, The method of claim 27. The passive NO ₂ based regeneration, the effective NO ₂ supplied active NO ₂ use is enhanced regeneration, simultaneously with at least one of the active _{O 2} based regeneration, the NO ₂ Use of the DPF using the recirculation NOx 32. The method of claim 31, wherein regeneration is performed. The passive NO ₂ based regeneration, the effective NO ₂ supplied active NO ₂ use is enhanced play, before at least one of the active _{O 2} based regeneration, the NO ₂ of the DPF using the recirculation NOx 32. The method of claim 31, wherein usage regeneration is performed. The passive NO ₂ based regeneration, the effective NO ₂ supplied active NO ₂ use is enhanced play, after at least one of the active _{O 2} based regeneration, the NO ₂ Use of the DPF using the recirculation NOx 32. The method of claim 31, wherein regeneration is performed.

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